Primidone in the long-term treatment of essential tremor: a prospective study with computerized quantitative analysis

Tips and tricks in tremor treatment

Tremor, whether arising from neurological diseases, other conditions, or medication side effects, significantly impacts patients' lives. Treatment complexities necessitate clear algorithms and strategies. Levodopa remains pivotal for Parkinson's tremor, though response variability exists. Some dopamine agonists offer notable tremor reduction targeting D2 receptors. Propranolol effectively manages essential tremor and essential tremor plus (ET/ET +), sometimes with primidone for added benefits, albeit dose-dependent side effects. As reserve medications anticholinergics and clozapine are used for treatment of parkinsonian tremor, 1-Octanol and certain anticonvulsant drugs for tremor of other orign, especially ET. Therapies such as invasive deep brain stimulation and lesional focused ultrasound serve for resistant cases. A medication review is crucial for all forms of tremor, but it is particularly important if medication may have triggered the tremor. Sensor-based detection and non-drug interventions like wristbands and physical therapy broaden diagnostic and therapeutic horizons, promising future tremor care enhancements. Understanding treatment nuances is a key for tailored tremor management respecting patient needs and tolerability. Successful strategies integrate pharmacological, non-invasive, and technological modalities, aiming for optimal symptom control and improved quality of life.

Cerebellar α6GABAA Receptors as a Therapeutic Target for Essential Tremor: Proof-of-Concept Study with Ethanol and Pyrazoloquinolinones

Ethanol has been shown to suppress essential tremor (ET) in patients at low-to-moderate doses, but its mechanism(s) of action remain unknown. One of the ET hypotheses attributes the ET tremorgenesis to the over-activated firing of inferior olivary neurons, causing synchronic rhythmic firings of cerebellar Purkinje cells. Purkinje cells, however, also receive excitatory inputs from granule cells where the α6 subunit-containing GABAA receptors (α6GABAARs) are abundantly expressed. Since ethanol is a positive allosteric modulator (PAM) of α6GABAARs, such action may mediate its anti-tremor effect. Employing the harmaline-induced ET model in male ICR mice, we evaluated the possible anti-tremor effects of ethanol and α6GABAAR-selective pyrazoloquinolinone PAMs. The burrowing activity, an indicator of well-being in rodents, was measured concurrently. Ethanol significantly and dose-dependently attenuated action tremor at non-sedative doses (0.4-2.4 g/kg, i.p.). Propranolol and α6GABAAR-selective pyrazoloquinolinones also significantly suppressed tremor activity. Neither ethanol nor propranolol, but only pyrazoloquinolinones, restored burrowing activity in harmaline-treated mice. Importantly, intra-cerebellar micro-injection of furosemide (an α6GABAAR antagonist) had a trend of blocking the effect of pyrazoloquinolinone Compound 6 or ethanol on harmaline-induced tremor. In addition, the anti-tremor effects of Compound 6 and ethanol were synergistic. These results suggest that low doses of ethanol and α6GABAAR-selective PAMs can attenuate action tremor, at least partially by modulating cerebellar α6GABAARs. Thus, α6GABAARs are potential therapeutic targets for ET, and α6GABAAR-selective PAMs may be a potential mono- or add-on therapy.

Non-Persistence of Tremorolytic Effect of Perampanel in Essential Tremor: Real-World Experience with 50 Patients

Background

We describe our experience of using perampanel to treat essential tremor (ET) over 12 months.

Methods

We enrolled 50 ET patients in an open-label trial. Perampanel was titrated to 4 mg/day as adjuvant therapy. The main outcome measures were baseline, +1, +3, +6, and + 12 month scores of the Tremor Clinical Rating Scale (TCRS) and the Glass scale (GS).

Results

Twenty patients withdrew because of adverse effects. At +1 month, 27 of 30 patients improved: 68% reduction in both TCRS 1 + 2 (P < 0.001) and TCRS 3 (P < 0.001); TCRS 4 + 1.8 and GS 1.1 point reduction. By +12 months non-persistence of therapeutic effect occurred in 70% of patients: the mean reduction in TCRS 1 + 2 was 33% (P = 0.03), TCRS 3 (0.04), TCRS 4 + 0.8, GS 0.2 points reduction.

Conclusions

We report important peramapanel acute tremorolytic effects, but poor tolerance to adverse effects and a non-sustained therapeutic effect in most patients.

4D printing of soft orthoses for tremor suppression

Tremor is an involuntary and oscillatory movement disorder that makes daily activities difficult for affected patients. Hand tremor-suppression orthoses are noninvasive, wearable devices designed to mitigate tremors. Various studies have shown that these devices are effective, economical, and safe; however, they have drawbacks such as large weight, awkward shape, and rigid parts. This study investigates different types of tremor-suppression orthoses and discusses their efficiency, mechanism, benefits, and disadvantages. First, various orthoses (with passive, semi-active, and active mechanisms) are described in detail. Next, we look at how additive manufacturing (AM) has progressed recently in making sensors and actuators for application in tremor orthoses. Then, the materials used in AM are further analyzed. It is found that traditional manufacturing problems can be solved with the help of AM techniques, like making orthoses that are affordable, lighter, and more customizable. Another concept being discussed is using smart materials and AM methods, such as four-dimensional (4D) printing, to make orthoses that are more comfortable and efficient.

Graphic abstract

Primidone Intolerance in Essential tremor: Is it More than Just Age?

Background:

There are few medications for the treatment of essential tremor (ET). One of these, primidone, which is one of only two front-line agents, is associated with considerable adverse drug reactions (ADRs). It is unclear why some primidone-treated ET patients develop ADRs whereas others do not, and why these ADRs seem to be more prevalent in ET patients than primidone-treated patients with epilepsy.

Objective:

To review several possible explanations underlying the above-referenced differences.

Methods:

A literature search was conducted in PubMed in October 2021. Studies reporting the ADRs of primidone in different neurological conditions were comprehensively reviewed.

Discussion:

Although there were no head-to-head data, a review of the previous studies on ET and epilepsy patients indicates that the former is relatively more intolerant to primidone. Moreover, not all ET patients develop ADR of similar nature or severity. We discuss several potential mechanisms for this variability in the intolerance to primidone. These include: (i) older age (ET vs. epilepsy patients), (ii) cross-tolerance to primidone in patients with epilepsy, (iii) neurobiological (GABA-related) abnormalities associated with ET.

Conclusion:

We speculate that there are several possible explanations for primidone intolerance in ET. These possibilities should be tested in future studies, and we propose the roadmap for designing these studies. It is of value to obtain detailed insight into these complex issues because primidone remains one of the few frontline anti-tremor medications in ET. Answers to issues we have raised in this article could facilitate more customized formulation of primidone in ET patients.

Prospective Tractography-Based Targeting for Improved Safety of Focused Ultrasound Thalamotomy

BACKGROUND

Focused ultrasound thalamotomy (FUS-T) was recently approved for the treatment of refractory essential tremor (ET). Despite its noninvasive approach, FUS-T reinitiated concerns about the adverse effects and long-term efficacy after lesioning.

OBJECTIVE

To prospectively assess the outcomes of FUS-T in 10 ET patients using tractography-based targeting of the ventral intermediate nucleus (VIM).

METHODS

VIM was identified at the intercommissural plane based on its neighboring tracts: the pyramidal tract and medial lemniscus. FUS-T was performed at the center of tractography-defined VIM. Tremor outcomes, at baseline and 3 mo, were assessed independently by the Tremor Research Group. We analyzed targeting coordinates, clinical outcomes, and adverse events. The FUS-T lesion location was analyzed in relation to unbiased thalamic parcellation using probabilisitic tractography. Quantitative diffusion-weighted imaging changes were also studied in fiber tracts of interest.

RESULTS

The tractography coordinates were more anterior than the standard. Intraoperatively, therapeutic sonications at the tractography target improved tremor (>50% improvement) without motor or sensory side effects. Sustained improvement in tremor was observed at 3 mo (tremor score: 18.3 ± 6.9 vs 8.1 ± 4.4, P = .001). No motor weakness and sensory deficits after FUS-T were observed during 6-mo follow-up. Ataxia was observed in 3 patients. FUS-T lesions overlapped with the VIM parcellated with probablisitic tractography. Significant microstructural changes were observed in the white matter connecting VIM with cerebellum and motor cortex.

CONCLUSION

This is the first report of prospective VIM targeting with tractography for FUS-T. These results suggest that tractography-guided targeting is safe and has satisfactory short-term clinical outcomes.

Current and Future Neuropharmacological Options for the Treatment of Essential Tremor

BACKGROUND

Essential Tremor (ET) is likely the most frequent movement disorder. In this review, we have summarized the current pharmacological options for the treatment of this disorder and discussed several future options derived from drugs tested in experimental models of ET or from neuropathological data.

METHODS

A literature search was performed on the pharmacology of essential tremors using PubMed Database from 1966 to July 31, 2019.

RESULTS

To date, the beta-blocker propranolol and the antiepileptic drug primidone are the drugs that have shown higher efficacy in the treatment of ET. Other drugs tested in ET patients have shown different degrees of efficacy or have not been useful.

CONCLUSION

Injections of botulinum toxin A could be useful in the treatment of some patients with ET refractory to pharmacotherapy. According to recent neurochemical data, drugs acting on the extrasynaptic GABAA receptors, the glutamatergic system or LINGO-1 could be interesting therapeutic options in the future.

Treatment of essential tremor: current status

Essential tremor is the most common cause of tremor involving upper limbs, head and voice. The first line of treatment for limb tremor is pharmacotherapy with propranolol or primidone. However, these two drugs reduce the tremor severity by only half. In medication refractory and functionally disabling tremor, alternative forms of therapy need to be considered. Botulinum toxin injections are likely efficacious for limb, voice and head tremor but are associated with side effects. Surgical interventions include deep brain stimulation; magnetic resonance-guided focused ultrasound and thalamotomy for unilateral and deep brain stimulation for bilateral procedures. Recent consensus classification for essential tremor has included a new subgroup, ‘Essential tremor plus’, who have associated subtle neurological ‘soft signs’, such as dystonic posturing of limbs and may require a different treatment approach. In this review, we have addressed the current management of essential tremor with regard to different anatomical locations of tremor as well as different modalities of treatment.

Essential tremor: diagnosis and management

Essential tremor is one of the most common movement disorders in adults and can affect both children and adults. An updated consensus statement in 2018 redefined essential tremor as an isolated action tremor present in bilateral upper extremities for at least three years. Tremor may also be present in other locations, commonly the neck or the vocal cords. Patients with additional neurologic symptoms are now categorized as "essential tremor plus." Additional clinical features associated with the condition include but are not limited to cognitive impairment, psychiatric disorders, and hearing loss. When treatment is needed, propranolol and primidone are considered first line treatments. Patients who are severely affected are often offered deep brain stimulation. Although the ventral intermediate nucleus of the thalamus is the traditional surgical target, the caudal zona incerta is also being studied as a possible superior alternative. Magnetic resonance imaging guided high intensity focused ultrasound is a newer surgical alternative that may be ideal for patients with substantial medical comorbidities. Current research explores novel oral treatments, chemodenervation, and noninvasive neuromodulation for treatment of essential tremor.

Need for mechanically and ergonomically enhanced tremor-suppression orthoses for the upper limb: a systematic review

INTRODUCTION

Tremor is the most common movement disorder, affecting 5.6% of the population with Parkinson's disease or essential tremor over the age of 65. Conventionally, tremor diseases like Parkinson's are treated with medication. An alternative non-invasive symptom treatment is the mechanical suppression of the oscillation movement. The purpose of this review is to identify the weaknesses of past wearable tremor-suppression orthoses for the upper limb and identify the need for further research and developments.

METHOD

A systematic literature search was conducted by performing a keyword combination search of the title, abstract and keyword sections in the four databases Web of Science, MedLine, Scopus, and ProQuest. Initially, the retrieved articles were selected by title and abstract using selection criteria. The same criteria were then applied to the full publication text. After the selection process, relevant information on the retrieved orthoses was isolated, sorted and analysed systematically.

RESULTS

Forty-six papers, representing 21 orthoses, were identified and analysed according to the mechanical and ergonomic properties. The identified orthoses can be divided into 5 concepts and 16 functional prototypes, then subdivided further based upon their use of passive, semi-active, or active suppression mechanisms. Most of the orthoses concentrate on the wrist and elbow flexion and extension. They mainly rely on rigid structures and actuators while having tremor-suppression efficacies for tremorous subjects from 30 to 98% using power spectral density or other methods.

CONCLUSION

The comparison of tremor-suppression orthoses considered and mapped their various mechanical and ergonomic properties, including the degrees of freedom, weight, suppression characteristics, and efficacies. This review shows that most of the orthoses are bulky and heavy, with a non-adapted human-machine interface which can cause rejection by the user. The main challenge of the design of an effective, minimally intrusive and portable tremor-suppressing orthosis is the integration of compact, powerful, lightweight, and non-cumbersome suppression mechanisms. None of the existing prototypes combine all the desired characteristics. Future research should focus on novel suppression orthoses and mechanisms with compact dimensions and light weight in order to be less cumbersome while giving a good tremor-suppression performance.

Current therapies and therapeutic decision making for childhood-onset movement disorders

Movement disorders differ in children to adults. First, neurodevelopmental movement disorders such as tics and stereotypies are more prevalent than parkinsonism, and second, there is a genomic revolution which is now explaining many early-onset dystonic syndromes. We outline an approach to children with movement disorders starting with defining the movement phenomenology, determining the level of functional impairment due to abnormal movements, and screening for comorbid psychiatric conditions and cognitive impairments which often contribute more to disability than the movements themselves. The rapid improvement in our understanding of the etiology of movement disorders has resulted in an increasing focus on precision medicine, targeting treatable conditions and defining modifiable disease processes. We profile some of the key disease-modifying therapies in metabolic, neurotransmitter, inflammatory, and autoimmune conditions and the increasing focus on gene or cellular therapies. When no disease-modifying therapies are possible, symptomatic therapies are often all that is available. These classically target dopaminergic, cholinergic, alpha-adrenergic, or GABAergic neurochemistry. Increasing interest in neuromodulation has highlighted that some clinical syndromes respond better to DBS, and further highlights the importance of "disease-specific" therapies with a future focus on individualized therapies according to the genomic findings or disease pathways that are disrupted. We summarize some pragmatic applications of symptomatic therapies, neuromodulation techniques, and some rehabilitative interventions and provide a contemporary overview of treatment in childhood-onset movement disorders. © 2019 International Parkinson and Movement Disorder Society.

Pharmacotherapy of essential tremor

Essential tremor (ET) is a common movement disorder but its pathogenesis remains poorly understood. This has limited the development of effective pharmacotherapy. The current therapeutic armamentaria for ET represent the product of careful clinical observation rather than targeted molecular modeling. Here we review their pharmacokinetics, metabolism, dosing, and adverse effect profiles and propose a treatment algorithm. We also discuss the concept of medically refractory tremor, as therapeutic trials should be limited unless invasive therapy is contraindicated or not desired by patients.

Update on treatment of essential tremor

OPINION STATEMENT

Essential tremor is one of the most common movement disorders in the world. Although millions of people worldwide are affected by ET, only one medication, propranolol, is approved by the United States Food and Drug Administration to treat it. None of the medications currently used as ET therapy were developed specifically for this purpose, and select antihypertensive and antiepileptic medications remain at the forefront of ET therapy. Propranolol and primidone are considered "effective" agents that treat ET; topiramate, atenolol, and alprazolam are "probably effective", and nimodipine, nadolol, and clonazepam are "possibly effective". Medications that probably do not adequately treat ET include levetiracetam and pregabalin. Gabapentin appears to improve ET when used as monotherapy, but not when used as adjunct therapy. Sotalol has been found to be "probably effective" in treating ET in previous reviews, but it may be associated with arrhythmias and should not be routinely recommended. Botulinum toxin A may reduce limb tremor, but may cause dose dependent weakness. Deep brain stimulation (DBS) of the VIM is used as an alternative to pharmacological therapy of ET in patients who fail to adequately respond to medical therapy. The magnitude of effect from DBS is greater than from medical management, but more severe side effects are possible with surgery. Future treatment options for ET will depend on valid animal models, and a better understanding of its pathophysiology.

Methodological issues in clinical drug development for essential tremor

Essential tremor (ET) is one of the most common tremor disorders in the world. Despite this, only two medications have received Level A recommendations from the American Academy of Neurology to treat it (primidone and propranolol). Even though these medications provide relief to a large group of ET patients, up to 50% of patients are non-responders. Additional medications to treat ET are needed. This review discusses some of the methodological issues that should be addressed for quality clinical drug development in ET.

Sustained Medication Reduction Following Unilateral VIM Thalamic Stimulation for Essential Tremor

BACKGROUND

Deep brain stimulation (DBS) is an increasingly utilized therapeutic modality for the management of medication refractory essential tremor (ET). The aim of this study was to determine whether DBS allowed for anti-tremor medication reduction within the year after the procedure was performed.

METHODS

We conducted a retrospective chart review and telephone interviews on 34 consecutive patients who had been diagnosed with ET, and who had undergone unilateral DBS surgery.

RESULTS

Of the 34 patients in our cohort, 31 patients (91%) completely stopped all anti-tremor medications either before surgery (21 patients, 62%) or in the year following DBS surgery (10 patients, 29%). Patients who discontinued tremor medications before DBS surgery did so because their tremors either became refractory to anti-tremor medication, or they developed adverse events to tremor medications. Patients who stopped tremor medications after DBS surgery did so due to sufficient tremor control. Only three patients (9%) who were taking tremor medications at the time of surgery continued the use of a beta-blocker post-operatively for the purpose of hypertension management in all cases.

DISCUSSION

The data from this study indicate that medication cessation is common following unilateral DBS for ET.

Treatment of Essential Tremor: Are there Issues We are Overlooking?

Background: Essential tremor (ET) is one of the most common neurological diseases. Although a large number of medications have been tested, there are only two first-line medications, primidone and propranolol, which is a situation that has not changed in approximately 30 years. Several recent reviews have summarized the current pharmacotherapeutic options for ET and the approach to the management of ET patients. Yet there remain a number of important issues, both scientific and clinical, that have not been broached in the literature and that have therapeutic implications. Objectives: To introduce several clinical and scientific issues that have not formally entered the published literature on the treatment of ET. Methods: In September 2011, materials for this article were gathered during a literature search of PubMed using the following terms: ET, clinical, clinical trial, treatment, medications, therapeutics. English-language articles were selected for further review. Results: The paper focuses on several topics that have received scant or no discussion in the published literature on ET therapeutics. These topics are as follows: the nature of the underlying disease pathophysiology, the presence of pathological heterogeneity, the complexity of cellular and neurochemical changes which may be underlying this disorder, the presence of clinical heterogeneity, the selection of treatment endpoints, the effects of diagnostic uncertainty, the presence of cognitive and psychiatric features in ET, the identification of possible modifiable risk factors, and the absence of any neuroprotective therapies. Conclusion: The author has identified several topics that have received scant or no discussion in the published literature on ET therapeutics. Further discussion of the issues raised here may lead to improvements in clinical trial methodologies as well as facilitate the development of fresh approaches to pharmacotherapy.

Diagnosis and management of essential tremor and dystonic tremor

Essential tremor (ET) is the most common adult movement disorder. Traditionally considered as a benign disease, it can cause an important physical and psychosocial disability. Drug treatment for ET remains poor and often unsatisfactory. Current therapeutic strategies for ET are reviewed according to the level of discomfort caused by tremor. For mild tremor, nonpharmacological strategies consist of alcohol and acute pharmacological therapy; for moderate tremor, pharmacological therapies (propranolol, gabapentin, primidone, topiramate, alprazolam and other drugs); and for severe tremor, the role of functional surgery is emphasised (thalamic deep brain stimulation, thalamotomy). The more specific treatment of head tremor with the use of botulinum toxin is also discussed. Several points are discussed to guide the immediate research into this disease in the near future. Dystonic tremor is a common symptom in dystonia. Diagnostic criteria for dystonic tremor and differential diagnosis with psychogenic tremor and ET are described. Treatment of dystonic tremor matches the treatment of dystonia. In cases of symptomatic dystonic tremor similar to ET, therapeutic strategies would be the same as for ET.

Management of essential tremor, including medical and surgical approaches

Essential tremor (ET) is one of the most common neurological disorders among adults. For many years, ET was viewed as a benign monosymptomatic condition, characterized by a kinetic arm tremor, yet over the last 10 years, a growing body of evidence suggests that this disorder is a progressive condition that is heterogeneous. Tremor may have a negative impact on health-related quality of life in some patients. Pharmacotherapy is initiated when the tremor interferes with the patient's ability to perform daily activities or when the tremor becomes embarrassing or affects health-related quality of life. For severe tremor, deep-brain stimulation of the thalamus may improve function.

Overview of essential tremor

Essential tremor (ET) is one of the most common movement disorders in the world. Despite this, only one medication (propranolol) is approved by the Food and Drug Administration (FDA) to treat it. Fortunately, recent studies have identified some additional medications as treatment of ET. Surgical procedures, such as deep brain stimulation of the ventral intermediate nucleus of the thalamus, offer treatment for refractory tremor. The epidemiology, pathogenesis, and medical and surgical treatment of ET will be discussed in this paper.

Survey of medication usage patterns among essential tremor patients: movement disorder specialists vs. general neurologists

BACKGROUND

Although small treatment trials have examined the efficacy of front-line medications in tremor reduction in essential tremor (ET), an overall survey of pharmacological management has not been undertaken in a large sample of ET cases.

OBJECTIVES

To conduct a survey of medication usage among several hundred ET patients.

METHODS

A computerized database at the Neurological Institute of New York was used to identify 223 ET patients cared for by movement disorder neurologists and 37 cared for by general neurologists. Each had been seen one or more times within past five years. Lifetime treatment data were abstracted from clinical records.

RESULTS

One-hundred-sixty-three (73.1%) of 223 patients cared for by movement disorder neurologists had taken medication for ET during their lifetime; 53/163 (32.5%) had taken ≥4 medications; 31/163 (19.0%) had taken ≥5 medications; and 3 (1.8%), ≥10 medications. Nearly three-quarters (158/223 [70.9%]) had taken primidone or propranolol, yet 89/158 (56.3%) had discontinued both. Among 11 patients who had undergone ET surgery, the mean number of ET medications tried was 6.0 ± 2.8 (range = 3-12). Medication usage by general neurologists was less than by movement disorder specialists (p < 0.001). One-third of general neurologists' patients (14/37 [37.8%]) had taken primidone or propranolol at some point and 6/14 (42.9%) had discontinued both.

CONCLUSIONS

In this large survey, a substantial proportion of ET patients failed treatment with both front-line medications. Among patients seeing movement disorder specialists, the number of medications they had had to try was sizable. These data demonstrate the limitations of current pharmacological options for ET.

Pharmacotherapy of essential tremor : an overview of existing and upcoming agents

Essential tremor is one of the most common movement disorders, yet the pharmacological treatments currently available have limited efficacy, being effective in only approximately 50% of patients with this disorder. The most commonly used, and generally most effective, medications for essential tremor are propranolol and primidone, administered either as monotherapy or in combination. If these medications do not provide satisfactory control of tremor, other beta-adrenoceptor antagonists, such as metoprolol or atenolol, and other antiepileptic drugs, such as topiramate or gabapentin, are often tried. In addition, benzodiazepines can be effective in some patients, particularly those with associated anxiety. There is a need for additional medications that result in greater tremor control in a larger number of patients with essential tremor. Several new drugs, including 1-octanol, sodium oxybate, dimethoxymethyl-diphenyl-barbituric acid (T-2000) and carisbamate, are currently under investigation for the treatment of essential tremor.

[Therapeutical strategies for essential tremor]

Essential tremor is the most common adult movement disorder. Traditionally considered as a benign disease, it can cause an important physical and psychosocial disability. Drug treatment remains poor and often unsatisfactory. Current therapeutical strategies are reviewed according to the level of discomfort caused by tremor: mild tremor, non-pharmacological strategies, alcohol, acute pharmacological therapy; moderate tremor, pharmacological therapies (propranolol, gabapentin, primidone, topiramate, alprazolam and other drugs), and severe tremor, the role of functional surgery is emphasized (thalamic deep brain stimulation, thalamotomy). It is also described the more specific treatment of head tremor with the use botulinum toxin. Finally, several points are exposed to guide the immediate research of this disease in near future.

Essential tremor

Essential tremor (ET) is among the most common neurologic disorders. The traditional view of this disorder as a benign, monosymptomatic, familial condition is being replaced by a more complex view of ET as perhaps a family of diseases with etiologic, clinical, and pathologic heterogeneity. This article discusses the major clinical features of ET and approaches to its diagnosis and treatment.

Essential tremor: emerging views of a common disorder

Essential tremor (ET) is the most prevalent tremor disorder. ET has traditionally been viewed as a monosymptomatic disorder characterized by a kinetic arm tremor, but this definition is gradually being replaced. The clinical spectrum has come to include several motor features, including tremor and ataxia, and several non-motor features, including possible cognitive impairment and personality disturbances. Postmortem studies are revealing several different patterns of pathology. The emerging view is that ET might be a family of diseases, unified by the presence of kinetic tremor, but further characterized by etiological, clinical and pathological heterogeneity. Effective pharmacological treatments for the disorder remain limited, although new insights into disease mechanisms might result in more-effective therapies. In addition, recent investigations of environmental toxicants that might be linked to ET open the way towards primary disease prevention through a reduction in exposure to these factors.

Interaction between blood lead concentration and delta-amino-levulinic acid dehydratase gene polymorphisms increases the odds of essential tremor

Blood lead (BPb) concentrations are elevated in essential tremor (ET) cases. The delta-amino-levulinic acid dehydratase (ALAD) gene codes for ALAD, the principal enzyme involved in lead kinetics. Carriers of the ALAD-2 allele may be more susceptible to lead toxicity. The objective of this study was to test, using a case-control design, whether an interaction between BPb concentration and ALAD allele status increases the odds of ET. Mean log BPb concentration was significantly higher in 63 cases than 101 controls (0.47+/-0.26 vs. 0.35+/-0.25 microg/dl). Eighteen (28.6%) cases vs. 17 (16.8%) controls had an ALAD-2 allele (OR=1.98; 95% CI=0.93--4.21). In an adjusted logistic regression analysis, the interaction term (ALAD allele status x log BPb concentration) was associated with increased odds for ET. In stratified analyses, log BPb concentration was not associated with odds of ET in individuals with two ALAD-1 alleles (OR=2.69; 95% CI=0.61--11.82), but in individuals with an ALAD-2 allele, BPb concentration was significantly associated with odds of ET (OR=80.29; 95% CI=3.08--2,096.36). There was an interaction between BPb concentration and ALAD allele status; the odds of ET were greatly elevated in individuals with both an ALAD-2 allele and an elevated BPb concentration. The presence of increased circulating BPb concentrations along with a greater potential for lead toxicity (ALAD-2 allele) could result in greater cerebellar damage, thereby increasing the risk of developing tremor.

Use of primidone in low doses (250 mg/day) versus high doses (750 mg/day) in the management of essential tremor. Double-blind comparative study with one-year follow-up

Essential tremor is the most common involuntary movement; we studied 113 affected subjects (54 men, 59 women) with an average age of 63.9 years and average duration of 9.05 years. These patients participated in a double-blind study with a 1-year follow-up to compare treatment efficiency using primidone dosages of 250 mg/day (G 250, 56 patients) versus 750 mg/day (G 750, 57 patients). The study was designed with an 80% power and 95% confidence level. The statistical analysis used was an ANOVA (with Bonferroni multiple comparison test corrections); a value of p<0.004 was accepted as significant. To compare other values, a chi-square test was used; p<0.05 was considered significant. To evaluate the efficacy of the drug, clinical protocol employed the 'clinical evaluation scale for tremor'. All of the patients were evaluated a total of 13 times, once prior to the introduction of primidone and the other 12 evaluations following the initiation of the treatment. Eighty-seven patients completed the study: 15 patients abandoned the study due to undesirable side effects, five due to negative response, and six who were lost to follow-up. The percentage of patients who didn't complete the study was significantly higher in the group that received 750 mg/day of primidone (p<0.04) and more frequent as well in this same group, due to undesirable side effects (p<0.03). The patients of both G250 and G750 showed a significant improvement in each of the controls compared to the basal value (p<0.0001). No significant differences (p<0.06) were found when the averages of the evaluations of each group were compared. These responses were maintained during the entire treatment period. Low doses of primidone (250 mg/day) were equally or more effective than high doses (750 mg/day) in the control of essential tremor; this response was maintained for 12 months and furthermore, demonstrated fewer undesirable effects.

Benefits and risks of pharmacological treatments for essential tremor

Essential tremor can cause significant functional disability in some patients. The arms are the most common body part affected and cause the most functional disability. The treatment of essential tremor includes medications, surgical options and other forms of therapy. Presently there is no cure for essential tremor nor are there any medications that can slow the progression of tremor. Treatment for essential tremor is recommended if the tremor causes functional disability. If the tremor is disabling only during periods of stress and anxiety, propranolol and benzodiazepines can be used during those periods when the tremor causes functional disability. The currently available medications can improve tremor in approximately 50% of the patients. If the tremor is disabling, treatment should be initiated with either primidone or propranolol. If either primidone or propranolol do not provide adequate control of the tremor, then the medications can be used in combination. If patients experience adverse effects with propranolol, occasionally other beta-adrenoceptor antagonists (such as atenolol or metoprolol) can be used. If primidone and propranolol do not provide adequate control of tremor, occasionally the use of benzodiazepines (such as clonazepam) can provide benefit. Other medications that may be helpful include gabapentin or topiramate. If a patient has disabling head or voice tremor, botulinum toxin injections into the muscles may provide relief from the tremor. Botulinum toxin in the hand muscles for hand tremor can result in bothersome hand weakness and is not widely used. There are other medications that have been tried in essential tremor and have questionable efficacy. These drugs include carbonic anhydrase inhibitors (e.g. methazolamide), phenobarbital, calcium channel antagonists (e.g. nimodipine), isoniazid, clonidine, clozapine and mirtazapine. If the patient still has disabling tremor after medication trials, surgical options are usually considered. Surgical options include thalamotomy and deep brain stimulation of the thalamus. These surgical options provide adequate tremor control in approximately 90% of the patients. Surgical morbidity and mortality for these procedures is low. Deep brain stimulation and thalamotomy have been shown to have comparable efficacy but fewer complications have been reported with deep brain stimulation. In patients undergoing bilateral procedures deep brain stimulation of the thalamus is the procedure of choice to avoid adverse effects seen with bilateral ablative procedures. The use of medication and/or surgery can provide adequate tremor control in the majority of the patients.

Essential tremor: differential diagnosis and current therapy

Essential tremor is a common movement disorder that affects between 5 and 10 million persons in the United States. It is characterized primarily by an action and postural tremor most often affecting the arms, but it can also affect other body parts. Essential tremor is a progressive neurologic disorder and can cause substantial disability in some patients. Although there is no cure for essential tremor, pharmacologic and surgical treatments can provide some benefit. Primidone and propranolol are first-line treatments. Other medications with potential efficacy include benzodiazepines, gabapentin, topiramate, and botulinum toxin. Patients with medication-resistant tremor may benefit from thalamotomy or deep brain stimulation of the thalamus. The use of medical and surgical therapies can provide benefit in up to 80% of patients with essential tremor.

Tremor--easily seen but difficult to describe and treat

Tremor is a common movement disorder yet many physicians struggle with its terminology as well as with its treatment. Attempts have been made to develop standard terminology and criteria for tremors but this process continues to evolve. In this review, a summary of the currently-proposed phenomenology and syndromic classification of all types of tremor is presented. The diagnosis and management of essential tremor is presented in more detail, as it is the most commonly encountered tremor.

2-deoxy-D-glucose attenuates harmaline induced tremors in rats

Neuronal hyperactivity in essential tremor is accompanied by high energy demand in cerebellum, medulla and the thalamus. It has been suggested that brain regions that have increased metabolic demands are highly vulnerable to interruptions in glucose metabolism. In the present investigation attempt was made to study the effect of 2-deoxyglucose (2DG) a glycolytic pathway inhibitor on harmaline induced tremor in rats. Wistar rats of either sex weighing 100+/-3 g were given harmaline (10 mg/kg, i.p.) alone or along with 2DG (15 min before harmaline) in doses of 300, 600 and 900 mg/kg, respectively. The latency of onset, intensity and duration of tremor following harmaline administration were recorded. Neurobehavioral responses, electromyography (EMG) and levels of blood glucose and cerebellar serotonin (5HT) were determined after 40 min of harmaline administration. 2DG significantly and dose dependently attenuated severity of harmaline induced tremors and amplitude of EMG. Treatment of rats with 2DG alone reduced the locomotor activity, however, no significant change was observed in grip strength, landing foot splay, air righting reflex and response to tactile stimuli. Harmaline alone and along with 2DG had no effect on behavioral parameters except a decrease in landing foot splay. 2DG produced a dose-dependent hyperglycemia and attenuated harmaline induced increase in cerebellar 5HT levels. Our results clearly suggest the protective effect of 2DG in harmaline induced tremor. Further studies are warranted to assess the role of glucoprivation in the suppression of neuronal excitability in tremors.

Management of essential tremor

Essential tremor (ET) is the most prevalent tremor syndrome. It commonly affects the hands, head, voice, and other body parts. Appropriate management begins with correct diagnosis. Primidone and propranolol are the first-line medications for the treatment for ET, but several other medications may also provide benefit. In patients with medically refractory tremor, alternative therapies, including surgery or injections of botulinum toxin, may be considered.

Randomized trial comparing primidone initiation schedules for treating essential tremor

Early side effects are common when primidone is used to treat essential tremor, with as many as one-third of patients failing to tolerate the tablets. Lower doses can be prescribed initially using a suspension formulation. We suspected suspension initiation would result in fewer early side effects, allow better acclimatization, and improve compliance. Forty patients with essential tremor were randomized to begin primidone treatment using either 2.5 mg doses in the suspension form or 25 mg doses in the tablet form. Doses gradually increased over 3 weeks to 150 mg/day. This was a double-blind, double-dummy trial. Medication cessation due to side effects was designated the primary end-point. Four patients in the suspension group and two in the tablet group dropped out due to early side effects, resulting in a relative risk of 1.9 (95% confidence interval 0.4 to 9.2). Side effects in the first 48 hours of treatment were equally common, affecting seven subjects in each group. Treatment benefits were the same in both groups. We concluded that use of a very low initial dose and a graduated titration schedule in suspension formulation did not appear to improve primidone tolerability. If anything, compliance tended to be worse when compared with the tablet formulation, though the study was under-powered to reject the null hypothesis of equivalence.

Phenomenology and treatment of tremor disorders

Tremor is classified according to anatomic distribution among body parts, and by frequency and amplitude during rest, postural maintenance, movement, intention, and the performance of specific tasks. Key historical features include age at onset, progression over time, family history, exacerbating and remitting factors and behaviors, response to alcohol and medications, and additional neurological signs and symptoms. Accurate diagnosis is a critical factor in predicting the natural history and response to treatment.

A teaching videotape for the assessment of essential tremor

Teaching videotapes, developed to aid in the evaluation of several movement disorders, have not been used in essential tremor research. As part of the Washington Heights-Inwood Genetic Study of Essential Tremor (WHIGET), we developed a reliable and valid tremor rating scale. Because this rating scale is currently being used by investigators at other centers, we developed a teaching videotape to aid in the consistent application of this scale.

OBJECTIVE

To develop a teaching videotape for a revised version of the WHIGET Tremor Rating Scale and to assess the interrater agreement among raters who used this videotape to rate tremor.

METHODS

The revised WHIGET Tremor Rating Scale was used to rate action tremor from 0 to 4 during six tests: arm extension, pouring, drinking, using a spoon, finger-to-nose, and drawing spirals. A 22-minute teaching videotape was developed that includes a 29-item educational section and a self-assessment section consisting of 20 examples of tremor ratings chosen by the two WHIGET study neurologists. Eight raters, including senior movement disorder specialists, movement disorder fellows, general neurologists, and a movement disorder nurse practitioner, independently viewed the videotape and rated tremor during the self-assessment section. Interobserver reliability was assessed with weighted kappa statistics (kappa(w)).

RESULTS

Eight raters each rated 20 items (160 ratings total). Total kappa(w) was 0.97 (nearly perfect agreement). Interrater reliability was as follows: kappa(w) = 0.99 (movement disorder specialists), kappa(w) = 0.98 (movement disorder fellows), and kappa(w) = 0.97 (general neurologists); all kappa(w) were nearly perfect.

CONCLUSIONS

This teaching videotape may be used to improve the uniform application of the revised WHIGET Tremor Rating Scale by raters with various levels of experience in movement disorders.

Validity and test-retest reliability of a disability questionnaire for essential tremor

BACKGROUND

One important outcome in clinical trials is patients' own opinions about whether the medication alleviates their symptoms and improves their ability to function. A valid and reliable method with which to assess this subjective information is important.

OBJECTIVE

To determine the validity and test-retest reliability of the Columbia University Disability Questionnaire for Essential Tremor (ET).

METHODS

Patients with ET underwent a 2.5-hour evaluation, including a 36-item tremor disability questionnaire, to assess the functional impact of tremor, a 26-item videotaped tremor examination rated by a neurologist, a 15-item performance-based test, and quantitative computerized tremor analysis. We determined the validity and test-retest reliability of the tremor disability questionnaire. Correlations between variables were assessed using Pearson's correlation coefficients and test-retest reliability with the weighted kappa statistic.

RESULTS

Ninety-five patients with ET participated. The score on tremor disability questionnaire correlated with the neurologist's clinical ratings (r = 0.57, p <0.001) and the total score on the performance-based test (r = 0.69, p < 0.001). Correlations with quantitative computerized tremor analysis results were less robust, but each remained significant, including mean amplitude of dominant arm tremor while arms were extended (r = 0.56, p <0.001), while drawing a spiral (r = 0.42, p = 0.01), and while pouring (r = 0.34, p = 0.04). The questionnaire was readministered to 32 subjects, and the test-retest reliability was substantial (weighted kappa = 0.67).

CONCLUSIONS

This Tremor Disability Questionnaire demonstrated substantial reliability, and it correlated with multiple measures of tremor severity, including a neurologist's clinical ratings, a performance-based test of function, and quantitative computerized tremor analysis results. The questionnaire would be useful in clinical trials in which it could be used as a reliable and valid tool to assess disability in ET.

Validation of a portable instrument for assessing tremor severity in epidemiologic field studies

BACKGROUND

An important part of epidemiologic and genetic studies of essential tremor (ET) is an assessment of tremor severity. Clinical rating scales are semiquantitative and computerized tremor analysis, available at tertiary medical centers, is not transportable into the field. As part of an epidemiologic study, we modified the Klove-Matthews Motor Steadiness Battery, collecting objective quantitative data on tremor severity in patients with ET and control subjects.

OBJECTIVE

To describe the modified Klove-Matthews Motor Steadiness Battery, validate this test battery against several other measures of tremor severity, demonstrate test-retest reliability, and provide standard reference values for normal control subjects and patients with ET who undergo this test battery.

METHODS

Patients with ET and control subjects, ascertained from both a clinic and a community, underwent a standardized evaluation including a demographic and medical questionnaire, tremor disability questionnaire, videotaped tremor examination, performance-based test, modified Klove-Matthews Motor Steadiness Battery (Groove-Type Steadiness Tester [GTST] and Nine-Hole Steadiness Tester [NHST]), and quantitative computerized tremor analysis.

RESULTS

There were 19 patients with ET and 28 control subjects. NHST and GTST total scores were correlated significantly with the tremor disability questionnaire score (r = 0.63, p = 0.001 and r = 0.49, p = 0.016), total tremor score (tremor examination, r = 0.68, p<0.001 and r = 0.41, p = 0.005), performance-based test score (r = 0.81, p<0.001 and r = 0.65, p = 0.001), and quantitative computerized tremor analysis results (for example, spiral drawing, r = 0.62, p = 0.01 and r = 0.58, p = 0.019). Test-retest reliability was generally high (r = 0.79-0.94, p<0.001).

CONCLUSION

The modified Klove-Matthews Motor Steadiness Battery provides a reliable and valid means to collect objective quantitative data on tremor severity. Rapidity of administration and ease of transport make it a potentially useful tool in epidemiologic and genetic field studies.

Pharmacologic treatment of tremor

Tremor is a common neurologic symptom that can also be incapacitating to the patient, so effective therapy is needed. The causes of tremor are heterogeneous. Essential tremor (ET) and the tremor associated with Parkinson's disease (PD) are the most common encountered in clinical practice. Beta-adrenergic blockers and primidone remain the mainstay of treatment for ET, whereas carbidopa/levodopa and anticholinergics are most beneficial in PD. However, the efficacy of various other medications has been studied in ET and PD, and also in patients with tremor resulting from other conditions, with varying results.

Mapping of a familial essential tremor gene, FET1, to chromosome 3q13

Essential tremor (ET), the most common movement disorder in humans, appears to be inherited as an autosomal dominant trait in many families. The familial form is called familial essential tremor (FET), which seems similar to sporadic essential tremor. ET is a cause of substantial disability, particularly in the elderly. The prevalence of Parkinson's disease and dystonia may be increased in families with ET, but other movement disorders are seldom encountered in these families. Here we report the results of a genome-wide scan for FET genes in 16 Icelandic families with 75 affected individuals, in whom FET was apparently inherited as a dominant trait. The scan, which was performed with a 10-cM framework map, revealed one locus on chromosome 3q13 to which FET mapped with a genome-wide significance when the data were analysed either parametrically, assuming an autosomal dominant model (lod score = 3.71), or non-parametrically (NPL Z score = 4.70, p < 6.4 x 10(-6).

Treatment of essential tremor with methazolamide

We treated 28 patients (16 women and 12 men) who had essential tremor with methazolamide. Their median age was 69 years (range, 34 to 89 years), and the median duration of tremor was 16 years (range, less than 1 to 69 years). Fifteen cases were familial and 13 were sporadic. Improvement in 10 patients who continued taking the drug ranged from moderate to complete relief. In addition, four patients had marked improvement and two had moderate improvement but discontinued use of the drug because of side effects. Five patients with a mild response and seven with no response also discontinued methazolamide therapy. The maximal mean daily dose was 203 mg for all patients and 129 mg (maintenance dose) for the patients who continued taking the drug. Side effects consisted primarily of somnolence, nausea, epigastric discomfort, anorexia, paresthesias, and numbness. No aplastic anemia was noted in any of the patients. The median duration of follow-up was 6 months (range, 10 weeks to 29 months). The therapeutic effect seemed unrelated to a family history of tremor, the effect of alcohol, or the responsiveness to propranolol or primidone. Methazolamide may be an effective drug in the treatment of some patients with essential tremor, particularly those with head and voice tremor.

Quantitative comparison of barbiturates in essential hand and head tremor

The tremorolytic effects of primidone and phenobarbital in essential tremor of hands and head were compared in a double-blind, placebo-controlled trial. Quantitative measurements of tremor were obtained in 15 patients by means of an accelerometric method. Only primidone proved to be superior to placebo in reducing hand tremor, suggesting that its tremorolytic effectiveness is largely dependent on the parent drug rather than its metabolite phenobarbital. Head tremor tended to improve only in three out of six patients with both primidone and phenobarbital, but, likely due to the small number of affected patients, the effect failed to reach statistical significance.